This invention relates in general to equipment used in conjunction with a microwave cavity, and more particularly to a restrictive insert for microwave cavities which are used in conjunction with food vending machines.
Since the development of the microwave ovens, a number of devices have been developed to aid in the heating of foods of various dimensions. For example, U.S. Pat. No. 3,091,172 (Wildemann), illustrates an apparatus in which it is possible to heat uniformly sausages or similarly elongated objects of different sizes and having different types of envelopes within the desired short time of about 15 seconds. In U.S. Pat. No. 3,283,113 (Smith), a small microwave oven suitable for use in vending machines for quickly cooking individual tubular units of the size and shape of frankfurter in a bun is disclosed. U.S. Pat. No. 2,733,650 (Williams) illustrates a microwave cooker to be incorporated in a vending machine. U.S. Pat. No. 2,820,127 (Argento) illustrates a microwave cavity having a plurality of slots on the side of the cavity and dimensions such that when the cavity is unloaded waste will be propagated in a particular mode which will cooperate with the slots, to pass energy out of the cavity through the slots, thus preventing its reflecting back into the cavity. U.S. Pat. No. 3,210,511 (Smith), describes an oven of small size suitable for heating single articles of food very quickly. U.S. Pat. No. 3,440,383 (Smith) discloses the use of a microwave device for heating food articles which includes a microwave source and a wave guide connected to the source with a normally open end adjacent to the food article. The food articles are contained in individual disposable containers including a conductive sheet surrounding all but one side of the container, the latter being permeable to the microwave energy. The containers are positioned with the permeable side adjacent to the open end of the waveguard, to extend the waveguide and enclose it around the food article, which serves as a load for the microwave energy. U.S. Pat. No. 3,665,491 (Cooper) illustrates a microwave oven divided into a plurality of zones. Each zone is operative to generate a different quantity of heat energy. Food trays are provided divided into a plurality of compartments, each adapted to be aligned with one of the oven zones so that the good disposed in that tray compartment is heated to the desired temperature. The primary disadvantage of these devices is that it requires the manufacture of a special type of oven and special types of vending dispensers, thus adding to the cost and complexity to the vending machine purveyors who desire to provide microwave heating service. Indeed, none of the devices referred to above have come into wide scale use in the United States in association with the purveying of foods from vending machines. Rather, the purveyors of food from vending machines use conventional microwave ovens, such as those used by a housewife, which has a relatively large cavity. The primary problem with the use of such an oven for the heating of sandwiches, etc., in a vending machine operation, is that there is no way of restricting access to the oven to only those people that have purchased food from the vending machine. Thus, it is not unusual to see persons that have purchased their sandwich from a vending machine waiting for a long period of time while some individual heats a casserole brought from his home. In addition to the inconvenience to the customer of the vending machine, the use of the microwave oven by people bringing foods from their homes tends to overload the machine since it is in use for longer periods of time.
Numerous accessories have been devised for use in microwave ovens. For example, U.S. Pat. No. 2,912,554 (Synder), illustrates the use of a metal sheel for electronic ovens constructed so that it does not absorb any appreciable quantity of the high frequency energy supplied to the oven. U.S. Pat. No. 2,997,566 (Pierce), shows a combination of deep fat fryer and microwave oven for cooking foodstuffs. U.S. Pat. No. 4,272,663 (Green) describes an apparatus for cooking steaks including a number of posts and two plates which are disposed in a sandwich configuration around a steak. The device is used to cook the steaks to the desired doneness. Also, U.S. Pat. No. 4,249,464 (Hansen), illustrates a rack to be placed in a microwave oven having a grid frame with open space allowing the dissipation of moisture. None of the devices described above are designed to deal with "problem of" unauthorized use of microwave ovens by noncustomers of vending machine operators.
Another patent of interest is U.S. Pat. No. 4,159,769 (Hatten) which illustrates a vending machine adaptor to allow items not normally suited to be vended through a particular vending machine to be vended. Hatten does not disclose any compatability with microwave ovens, nor is the design to restrict the accessibility of a microwave oven.